检索结果-南通市图书馆

Underwater four-quadrant dual-beam circumferential scanning laser fuze using nonlinear adaptive backscatter filter based on pauseable SAF-LMS algorithm

在线全文

学校读者我要写书评

暂无评论

Defence Technology（防务技术） 2024年第7期37卷 1-13页

作者： guangbo Xu Bingting zha Hailu Yuan Zhen Zheng He zha.g Ministerial Key Laboratory of ZNDY Nanjing University of Science and TechnologyNanjing 210094China Science and Technology on Electromechanical Dynamic Control Laboratory Beijing 100081China Shanghai Radio Equipment Research Institute Shanghai 201109China

The phenomenon of a target echo peak overlapping with the backscattered echo peak significantly undermines the detection range and precision of underwater laser *** overcome this issue,we propose a four-quadrant dual-beam circumferential scanning laser fuze to distinguish various interference signals and provide more real-time data for the backscatter filtering *** enhances the algorithm loading capability of the *** order to address the problem of insufficient filtering capacity in existing linear backscatter filtering algorithms,we develop a nonlinear backscattering adaptive filter based on the spline adaptive filter least mean square(SAF-LMS)*** also designed an algorithm pause module to retain the original trend of the target echo peak,improving the time discrimination accuracy and anti-interference capability of the ***,experiments are conducted with varying signal-to-noise ratios of the original underwater target echo *** experimental results show that the average signal-to-noise ratio before and after filtering can be improved by more than31 d B,with an increase of up to 76%in extreme detection distance.

关键词： Laser fuze Underwater laser detection Backscatter adaptive filter Spline least mean square algorithm Nonlinear filtering algorithm

Current trajectory image-based protection algorithm for transmission lines connected to MMC-HVDC stations using CA-CNN

在线全文

学校读者我要写书评

暂无评论

Protection and Control of Modern Power Systems 2023年第1期8卷 97-111页

作者： Yingyu Liang Yi Ren Jinhua Yu Wenting zha School of Mechanical Electronic and Information Engineering China University of Mining and Technology(Beijing) Beijing 100083China

In the presence of an MMC-HVDC system,current differential protection(CDP)has the risk of failure in operation under an internal *** addition,CDP may also incur security issues in the presence of current transformer(CT)saturation and *** this paper,a current trajectory image-based protection algorithm is proposed for AC lines connected to MMC-HVDC stations using a convolution neural network improved by a channel attention mechanism(CA-CNN).Taking the dual differential currents as two-dimensional coordinates of the moving point,the moving-point trajectories formed by differential currents have significant differences under internal and external ***,internal faults can be identified using image recognition based on *** is improved by a channel attention mechanism,data augmentation,and adaptive learning *** comparison with other machine learning algorithms,the feature extraction ability and accuracy of CA-CNN are greatly *** fault conditions like different net-work structures,operation modes,fault resistances,outliers,and current transformer saturation,are fully considered to verify the superiority of the proposed protection *** results confirm that the proposed current trajectory image-based protection algorithm has strong learning and generalizability,and can identify internal faults reliably.

关键词： Channel attention mechanism Convolutional neural network(CNN) Differential current Current trajectory image Modular multilevel converter-based high voltage direct current(MMC-HVDC)

A FINITE DEFORMATION ANALYSIS OF POLYCRYSTAL BY CONSIDERINg THE INFLUENCE OF gRAIN BOUNDARY

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Acta Mechanica Solida Sinica 1996年第3期9卷 189-200页

作者： Pan, wk zha.g, YW Wang, TC UNIV SCI & TECHNOL CHINA HEFEI 230026PEOPLES R CHINA CHINESE ACAD SCI INST MECHBEIJING 100080PEOPLES R CHINA

By combining grain boundary (gB) and its influence zone, a micromechanic model for polycrystal is established for considering the influence of gB. By using the crystal plasticity theory and the finite element method for finite deformation, numerical simulation is carried out by the model. Calculated results display the microscopic characteristic of deformation fields of grains and are in qualitative agreement with experimental results.

关键词： grain boundary slip slid crystal plasticity finite deformation

An Algorithm for Determination of Projectile Attitude Angles in Projectile Trajectory Prediction

在线全文

学校读者我要写书评

暂无评论

Transactions of Nanjing University of Aeronautics and Astronautics 2018年第2期35卷 361-370页

作者： zha Qicheng Rui Xiaoting Yu Hailong Zhou Qinbo Institute of Launch Dynamics School of Energy and Power EngineeringNanjing University of Science and Technology

A fast and accurate algorithm is established in this paper to increase the precision of ballistic trajectory *** algorithm is based on the six-degree-of-freedom(6 DOF)trajectory equations,to estimate the projectile attitude angles in every measuring ***,the algorithm utilizes the Davidon-Fletcher-Powell(DFP)method to solve nonlinear equations and Doppler radar trajectory test information containing only position coordinates of the projectile to reconstruct the angular ***″position coordinates by the test″and″angular displacements by reconstruction″at the end phase of the radar measurement are used as an initial value for the trajectory computation to extrapolate the trajectory impact *** numerical simulations validate the proposed method and demonstrate that the estimated impact point agrees very well with the real ***,other artillery trajectory can be predicted by the algorithm,and other trajectory models,such as 4 DOF and 5 DOF models,can also be incorporated into the proposed algorithm.

关键词： ballistic trajectory impact point prediction Davidon-Fletcher-Powell method six-degree-of-freedom trajectory model Doppler radar data

A New Network Coding Mechanism Balancing Coding Opportunities, Energy and QoS in WSNs

在线全文

学校读者我要写书评

暂无评论

China Communications 2014年第6期11卷 108-118页

作者： ZHENg Kangfeng WANg Xiujuan zha Xuan XIAO Huan School of Computer Science Beijing University of Posts and Telecommunications School of Computer Science Beijing University of Technology

A new Network Coding mechanism in WSNs(Wireless Sensor Networks), which is named COEQ and aims at balancing coding opportunities, energy and QoS, is proposed and analyzed. Implemented on the basis of traditional AODV protocol, COEQ evaluates several metrics of paths comprehensively with TOPSIS method including minimum remaining energy, coding opportunities, QoS and so on, so as to select the optimal transmitting route. Experiments on NS[2] show that COEQ can improve throughput and save energy when the transmitting rate is low.

关键词： network coding wireless sensor network QoS TOPSIS

A curvelet-based method to determine wave directions from nautical X-band radar images

在线全文

学校读者我要写书评

暂无评论

Acta Oceanologica Sinica 2018年第1期37卷 11-19页

作者： zha.guozhen HE Qingyou gUAN Changlong CHEN Jitao College of Oceanic and Atmospheric Sciences Ocean University of China Qingdao 266100 China Physical Oceanography Laboratory Ocean University of China Qingdao 266100 China State Key Laboratory of Tropical Oceanography South China Sea Institute of Oceanology Chinese Academy of Science Guangzhou 510301 China Hydrology Bureau of Yellow River Conservancy Commission Zhengzhou 450004 China

A new method to determine wave directions from nautical X-band images is proposed. The signatures of ocean waves show obvious scale and directional characteristics in nautical X-band radar images. Curvelet transform（CT） possesses very high scale and directional sensitivities. Therefore, it has good capability to analyze ocean wave fields. The radar images are decomposed at different scales, in different directions, and at different positions by CT, and curvelet coefficients are obtained. given to the scale and directional characteristics of surface waves,the information of ocean waves is centralized in the curvelet coefficients of certain directions and at certain ***, the wave orientations can be determined. The 180 ambiguity is removed by calculating crosscorrelation coefficients（CCCs） between continuous collected images. The proposed method is verified by the dataset collected on the Northwest coast of the zha.gzi Island in the Yellow Sea of China from March to April 2009.

关键词： X-band radar wave direction surface wave curvelet transform

A Novel Provable Data Possession Scheme Based on geographic Location Attribute

在线全文

学校读者我要写书评

暂无评论

China Communications 2016年第9期13卷 139-150页

作者： Yaxing zha Shoushan Luo Jianchao Bian Wei Li National Engineering Laboratory of Disaster Backup and Recovery Beijing University of Posts and TelecommunicationsBeijing 100876China Information Security Center Beijing University of Posts and TelecommunicationsBeijing 100876China

Increment of mobile cloud video motivates mobile users to utilize cloud storage service to address their demands, cloud storage provider always furnish a location-independent platform for managing user＇s data. However, mobile users wonder if their cloud video data leakage or dynamic migration to illegal service providers. In this paper, we design a novel provable data possession protocol based on data geographic location attribute, which allows data owner to auditing the integrity of their video data, which put forward an ideal choice for remote data possession checking in the mobile cloud storage. In our proposed scheme, we check out whether the video data dynamic migrate to an unspecified location （such as： overseas） by adding data geographic location attribute tag into provable data possession protocol. Moreover, we make sure the security of our proposed scheme under the Computational Diffic-Hellman assumption. The analysis and experiment results demonstrate that our proposed scheme is provably secure and efficient.

关键词： cloud storage security provable data possession geographic location security boundary CDH assumption

PPP-RTK functional models formulated with undiferenced and uncombined gNSS observations

在线全文

学校读者我要写书评

暂无评论

Satellite Navigation 2022年第1期3卷 139-153,I0005页

作者： Baocheng zha.g Pengyu Hou Jiuping zha Teng Liu State Key Laboratory of geodesy and Earth’s Dynamics Innovation Academy for Precision Measurement Science and TechnologyChinese Academy of SciencesWuhanChina College of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijingChina State Key Laboratory of Satellite Navigation System and Equipment Technology The 54th Research Institute of China Electronics Technology Group CorporationShijiazhuangChina

Technique PPP-RTK combines the advantages of both the Precise Point Positioning(PPP)and the Real-Time Kinematic(RTK)*** the emergence of multi-frequency global Navigation Satellite System(gNSS)observations,it is preferable to formulate PPP-RTK functional models based on original(undiferenced and uncombined)*** there exist many variants of the undiferenced and uncombined PPP–RTK models,a unifed theoretical framework needs developing to link these *** this contribution,we formulate a class of undiferenced and uncombined PPP-RTK functional models in a systematic way and cast them in a unifed *** framework classifes the models into a code-plus-phase category and a phase-only *** category covers a variety of measurement scenarios on the network side,ranging from small-,medium-to large-scale *** each scenario,special care has been taken of the distinct ionospheric constraints and the diference between Code Division Multiple Access(CDMA)and Frequency Division Multiple Access(FDMA)*** key to systematically formulating these models lies in how to deal with the rank defciency problems *** opt for the Singularity-basis(S-basis)theory,giving rise to the full-rank observation equations in which the estimable parameters turn out to be the functions of original parameters and those selected as the *** the sequel,it becomes straightforward to derive for each scenario the user model as it,more or less,amounts to the single-receiver network *** from the presented theoretical framework,the relationships and diferences between various undiferenced and uncombined PPP-RTK models become clear,which can lead to the better use of these models in a specifc situation.

关键词： global navigation satellite system(gNSS) Ambiguity resolution-enabled precise point positioning(PPP-RTK) Singularity-basis(S-basis) Undiferenced and uncombined Frequency division multiple access(FDMA) Phaseonly

A Hybrid MCDM Approach Based on ANP and TOPSIS for Facility Layout Selection

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Transactions of Nanjing University of Aeronautics and Astronautics 2018年第6期35卷 1027-1037页

作者： zha Shanshan guo Yu Huang Shaohua Tang Pengzhou College of Mechanical and Electrical Engineering Nanjing University of Aeronautics and Astronautics

Facility layout selection is a multi-criteria decision making (MCDM) problem,since it has a strategic impact on the efficiency of manufacturing *** view of the interdependency among selection criteria,analytic network process (ANP) is proposed to analyze the structure of the facility layout selection problem and determine the weights for each criterion.A network structure is constructed that shows all elements and clusters and their *** priorities are also calculated which help decision maker evaluate the relative importance among criterion in the alternative selection ***,a hybrid MCDM approach that employs ANP and technique for order preference by similarity to an ideal solution (TOPSIS)method to rank the optimal facility layout ***,an application of a new aeronautic component assembly workshop facility layout selection is *** further illustrate the advantage of the proposed approach,the difference between ANP-TOPSIS and AHP-TOPSIS methods are compared and *** have demonstrated the effectiveness and feasibility of the proposed method.

关键词： facility layout selection multi-criteria decision making(MCDM) analytic network process AHP TOPSIS